The United States accounts for the largest domestic letter traffic in the world, handling almost 200 billion pieces of mail each year. The United States Postal Service (USPS) employs more than 850,000 employees and operates more than 44,000 post offices throughout the country. In many respects, the economy of the country is dependent upon the postal system being able to efficiently and quickly deliver mail pieces. Any type of major disruption in the delivery of mail could have potentially serious detrimental effects on the country as a whole.
Recently, attempts have been made to disrupt the postal system and use it as a weapon of terror and fear by the inclusion of harmful chemical or biological contaminants, such as, for example, the spore-forming bacterium Bacillus anthracis (anthrax), within or on a mail piece. Such contaminants can be carried in several forms, including for example, a powder form. The harmful effects of only a few contaminated mail pieces can be far reaching, as cross-contamination of other mail pieces can easily occur when the mail pieces come in contact with each other or are passed through the same machines during sorting. The Centers for Disease Control and Prevention estimates that tens of thousands of mail pieces could have become cross-contaminated from only two contaminated mail pieces. The use of the postal system for such purposes has resulted in the need for a reliable way to detect mail pieces suspected of being contaminated before they are processed by the postal authority, thereby significantly reducing any cross-contamination by the contaminated mail pieces.
Ideally, it would be desirous for the postal authority to examine and/or test each piece of mail individually for any possible contaminants before it enters the mail system, thereby isolating any contaminated mail pieces and preventing any cross-contamination. If a suspected mail piece is found, it would also be desirous to be able to identify any other mail pieces that have similar attributes, and therefore may have been sent by the same sender of the suspected contaminated mail piece, and remove them from the mail processing stream for inspection as well. By removing other mail pieces with similar attributes to a suspect mail piece, cross-contamination can be prevented if, in fact, the other mail pieces are also contaminated. Even if the other mail pieces are not contaminated, it may still be possible to collect evidence, based on the other non-contaminated similar mail pieces, with respect to the actual origin and sender of the contaminated mail piece. With the large volume of mail processed daily and the large number of post offices where mail is inducted into the postal system, however, it is currently not possible to timely and cost effectively identify any mail pieces that have similar attributes to a suspected contaminated mail piece. It is imperative that any such identification be capable of being performed both cost effectively and quickly to avoid delays in processing and delivering the mail.
Thus, there exists a need for a reliable way that quickly and cost effectively identifies mail pieces that are similar to mail pieces suspected of being contaminated.